1. Field of the Invention
This invention generally relates to aperture apparatuses for use in optical apparatuses, and more particularly, to an aperture apparatus suitable for use in an optical apparatus such as a digital camera, camcorder, or the like.
2. Description of the Related Art
Conventionally, there have been proposed aperture apparatuses mounted on cameras. It is well known that an aperture apparatus includes multiple aperture blades driven by a drive ring to realize a multi-step aperture mechanism of five or more steps. It is also well known that an aperture apparatus that realizes a given small aperture state by shielding a lens opening with a small aperture blade having a small aperture opening. The aperture apparatus having the drive ring generally has a complex structure, and tends to be large in size. Therefore, it is used for a high-grade camera. However, in these years, low-cost cameras and digital cameras are widely used. For this reason, there is a rising demand for the aperture apparatus whose aperture mechanism is limited to two to four steps, structure is simple, and size is further reduced.
As disclosed in Japanese Patent Application Publication No. 2001-188276 (hereinafter, referred to as Patent Document 1), for example, the aperture apparatus is downsized by reducing and limiting the number of aperture steps. In the aperture apparatus disclosed in Patent Document 1, two small aperture blades having different small aperture openings are swingablly located. Then, a drive pin selectively drives the two small aperture blades to shield the lens opening and form a fully open state, a first small aperture state, and a second small aperture state. Such aperture apparatus is capable of forming two steps of the small aperture state.
The aperture apparatus disclosed in Patent Document 1, however, utilizes the drive pin only for moving the aperture blades to a lens opening position. Accordingly, a return spring is also provided to return the aperture blades to a waiting position (or receding position). Also, a stop position deciding pin is provided so that the aperture blade to which a biasing force is applied may stop at a given waiting position. With the afore-described configuration, the biasing force of the return spring is always working on the aperture blade. So, it is needed to employ a large actuator that drives the drive pin in consideration of the load. In addition, the stop position deciding pin (stop position deciding member) has to be provided at the waiting position to stop the aperture blade, thereby increasing the number of components.